fs/char_dev.c

   1 /*
   2  *  linux/fs/char_dev.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/config.h>
   8 #include <linux/init.h>
   9 #include <linux/fs.h>
  10 #include <linux/slab.h>
  11 #include <linux/string.h>
  12
  13 #include <linux/major.h>
  14 #include <linux/string.h>
  15 #include <linux/errno.h>
  16 #include <linux/module.h>
  17 #include <linux/smp_lock.h>
  18 #include <linux/devfs_fs_kernel.h>
  19
  20 #include <linux/kobject.h>
  21 #include <linux/kobj_map.h>
  22 #include <linux/cdev.h>
  23
  24 #ifdef CONFIG_KMOD
  25 #include <linux/kmod.h>
  26 #endif
  27
  28 static struct kobj_map *cdev_map;
  29
  30 #define MAX_PROBE_HASH 255      /* random */
  31
  32 static rwlock_t chrdevs_lock = RW_LOCK_UNLOCKED;
  33
  34 static struct char_device_struct {
  35         struct char_device_struct *next;
  36         unsigned int major;
  37         unsigned int baseminor;
  38         int minorct;
  39         const char *name;
  40         struct file_operations *fops;
  41         struct cdev *cdev;              /* will die */
  42 } *chrdevs[MAX_PROBE_HASH];
  43
  44 /* index in the above */
  45 static inline int major_to_index(int major)
  46 {
  47         return major % MAX_PROBE_HASH;
  48 }
  49
  50 /* get char device names in somewhat random order */
  51 int get_chrdev_list(char *page)
  52 {
  53         struct char_device_struct *cd;
  54         int i, len;
  55
  56         len = sprintf(page, "Character devices:\n");
  57
  58         read_lock(&chrdevs_lock);
  59         for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
  60                 for (cd = chrdevs[i]; cd; cd = cd->next)
  61                         len += sprintf(page+len, "%3d %s\n",
  62                                        cd->major, cd->name);
  63         }
  64         read_unlock(&chrdevs_lock);
  65
  66         return len;
  67 }
  68
  69 /*
  70  * Register a single major with a specified minor range.
  71  *
  72  * If major == 0 this functions will dynamically allocate a major and return
  73  * its number.
  74  *
  75  * If major > 0 this function will attempt to reserve the passed range of
  76  * minors and will return zero on success.
  77  *
  78  * Returns a -ve errno on failure.
  79  */
  80 static struct char_device_struct *
  81 __register_chrdev_region(unsigned int major, unsigned int baseminor,
  82                            int minorct, const char *name)
  83 {
  84         struct char_device_struct *cd, **cp;
  85         int ret = 0;
  86         int i;
  87
  88         cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL);
  89         if (cd == NULL)
  90                 return ERR_PTR(-ENOMEM);
  91
  92         memset(cd, 0, sizeof(struct char_device_struct));
  93
  94         write_lock_irq(&chrdevs_lock);
  95
  96         /* temporary */
  97         if (major == 0) {
  98                 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
  99                         if (chrdevs[i] == NULL)
 100                                 break;
 101                 }
 102
 103                 if (i == 0) {
 104                         ret = -EBUSY;
 105                         goto out;
 106                 }
 107                 major = i;
 108                 ret = major;
 109         }
 110
 111         cd->major = major;
 112         cd->baseminor = baseminor;
 113         cd->minorct = minorct;
 114         cd->name = name;
 115
 116         i = major_to_index(major);
 117
 118         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 119                 if ((*cp)->major > major ||
 120                     ((*cp)->major == major && (*cp)->baseminor >= baseminor))
 121                         break;
 122         if (*cp && (*cp)->major == major &&
 123             (*cp)->baseminor < baseminor + minorct) {
 124                 ret = -EBUSY;
 125                 goto out;
 126         }
 127         cd->next = *cp;
 128         *cp = cd;
 129         write_unlock_irq(&chrdevs_lock);
 130         return cd;
 131 out:
 132         write_unlock_irq(&chrdevs_lock);
 133         kfree(cd);
 134         return ERR_PTR(ret);
 135 }
 136
 137 static struct char_device_struct *
 138 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
 139 {
 140         struct char_device_struct *cd = NULL, **cp;
 141         int i = major_to_index(major);
 142
 143         write_lock_irq(&chrdevs_lock);
 144         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 145                 if ((*cp)->major == major &&
 146                     (*cp)->baseminor == baseminor &&
 147                     (*cp)->minorct == minorct)
 148                         break;
 149         if (*cp) {
 150                 cd = *cp;
 151                 *cp = cd->next;
 152         }
 153         write_unlock_irq(&chrdevs_lock);
 154         return cd;
 155 }
 156
 157 int register_chrdev_region(dev_t from, unsigned count, char *name)
 158 {
 159         struct char_device_struct *cd;
 160         dev_t to = from + count;
 161         dev_t n, next;
 162
 163         for (n = from; n < to; n = next) {
 164                 next = MKDEV(MAJOR(n)+1, 0);
 165                 if (next > to)
 166                         next = to;
 167                 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
 168                                next - n, name);
 169                 if (IS_ERR(cd))
 170                         goto fail;
 171         }
 172         return 0;
 173 fail:
 174         to = n;
 175         for (n = from; n < to; n = next) {
 176                 next = MKDEV(MAJOR(n)+1, 0);
 177                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 178         }
 179         return PTR_ERR(cd);
 180 }
 181
 182 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, char *name)
 183 {
 184         struct char_device_struct *cd;
 185         cd = __register_chrdev_region(0, baseminor, count, name);
 186         if (IS_ERR(cd))
 187                 return PTR_ERR(cd);
 188         *dev = MKDEV(cd->major, cd->baseminor);
 189         return 0;
 190 }
 191
 192 int register_chrdev(unsigned int major, const char *name,
 193                     struct file_operations *fops)
 194 {
 195         struct char_device_struct *cd;
 196         struct cdev *cdev;
 197         char *s;
 198         int err = -ENOMEM;
 199
 200         cd = __register_chrdev_region(major, 0, 256, name);
 201         if (IS_ERR(cd))
 202                 return PTR_ERR(cd);
 203
 204         cdev = cdev_alloc();
 205         if (!cdev)
 206                 goto out2;
 207
 208         cdev->owner = fops->owner;
 209         cdev->ops = fops;
 210         strcpy(cdev->kobj.name, name);
 211         for (s = strchr(cdev->kobj.name, '/'); s; s = strchr(s, '/'))
 212                 *s = '!';
 213
 214         err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
 215         if (err)
 216                 goto out;
 217
 218         cd->cdev = cdev;
 219
 220         return major ? 0 : cd->major;
 221 out:
 222         kobject_put(&cdev->kobj);
 223 out2:
 224         kfree(__unregister_chrdev_region(cd->major, 0, 256));
 225         return err;
 226 }
 227
 228 void unregister_chrdev_region(dev_t from, unsigned count)
 229 {
 230         dev_t to = from + count;
 231         dev_t n, next;
 232
 233         for (n = from; n < to; n = next) {
 234                 next = MKDEV(MAJOR(n)+1, 0);
 235                 if (next > to)
 236                         next = to;
 237                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 238         }
 239 }
 240
 241 int unregister_chrdev(unsigned int major, const char *name)
 242 {
 243         struct char_device_struct *cd;
 244         cdev_unmap(MKDEV(major, 0), 256);
 245         cd = __unregister_chrdev_region(major, 0, 256);
 246         if (cd && cd->cdev)
 247                 cdev_del(cd->cdev);
 248         kfree(cd);
 249         return 0;
 250 }
 251
 252 static spinlock_t cdev_lock = SPIN_LOCK_UNLOCKED;
 253 /*
 254  * Called every time a character special file is opened
 255  */
 256 int chrdev_open(struct inode * inode, struct file * filp)
 257 {
 258         struct cdev *p;
 259         struct cdev *new = NULL;
 260         int ret = 0;
 261
 262         spin_lock(&cdev_lock);
 263         p = inode->i_cdev;
 264         if (!p) {
 265                 struct kobject *kobj;
 266                 int idx;
 267                 spin_unlock(&cdev_lock);
 268                 kobj = kobj_lookup(cdev_map, kdev_t_to_nr(inode->i_rdev), &idx);
 269                 if (!kobj)
 270                         return -ENODEV;
 271                 new = container_of(kobj, struct cdev, kobj);
 272                 spin_lock(&cdev_lock);
 273                 p = inode->i_cdev;
 274                 if (!p) {
 275                         inode->i_cdev = p = new;
 276                         inode->i_cindex = idx;
 277                         list_add(&inode->i_devices, &p->list);
 278                         new = NULL;
 279                 } else if (!cdev_get(p))
 280                         ret = -ENODEV;
 281         } else if (!cdev_get(p))
 282                 ret = -ENODEV;
 283         spin_unlock(&cdev_lock);
 284         cdev_put(new);
 285         if (ret)
 286                 return ret;
 287         filp->f_op = fops_get(p->ops);
 288         if (!filp->f_op) {
 289                 cdev_put(p);
 290                 return -ENODEV;
 291         }
 292         if (filp->f_op->open) {
 293                 lock_kernel();
 294                 ret = filp->f_op->open(inode,filp);
 295                 unlock_kernel();
 296         }
 297         if (ret)
 298                 cdev_put(p);
 299         return ret;
 300 }
 301
 302 void cd_forget(struct inode *inode)
 303 {
 304         spin_lock(&cdev_lock);
 305         list_del_init(&inode->i_devices);
 306         inode->i_cdev = NULL;
 307         spin_unlock(&cdev_lock);
 308 }
 309
 310 void cdev_purge(struct cdev *cdev)
 311 {
 312         spin_lock(&cdev_lock);
 313         while (!list_empty(&cdev->list)) {
 314                 struct inode *inode;
 315                 inode = container_of(cdev->list.next, struct inode, i_devices);
 316                 list_del_init(&inode->i_devices);
 317                 inode->i_cdev = NULL;
 318         }
 319         spin_unlock(&cdev_lock);
 320 }
 321
 322 /*
 323  * Dummy default file-operations: the only thing this does
 324  * is contain the open that then fills in the correct operations
 325  * depending on the special file...
 326  */
 327 struct file_operations def_chr_fops = {
 328         .open = chrdev_open,
 329 };
 330
 331 const char *cdevname(kdev_t dev)
 332 {
 333         static char buffer[40];
 334         const char *name = "unknown-char";
 335         unsigned int major = major(dev);
 336         unsigned int minor = minor(dev);
 337         int i = major_to_index(major);
 338         struct char_device_struct *cd;
 339
 340         read_lock(&chrdevs_lock);
 341         for (cd = chrdevs[i]; cd; cd = cd->next)
 342                 if (cd->major == major)
 343                         break;
 344         if (cd)
 345                 name = cd->name;
 346         sprintf(buffer, "%s(%d,%d)", name, major, minor);
 347         read_unlock(&chrdevs_lock);
 348
 349         return buffer;
 350 }
 351
 352 static struct kobject *exact_match(dev_t dev, int *part, void *data)
 353 {
 354         struct cdev *p = data;
 355         return &p->kobj;
 356 }
 357
 358 static int exact_lock(dev_t dev, void *data)
 359 {
 360         struct cdev *p = data;
 361         return cdev_get(p) ? 0 : -1;
 362 }
 363
 364 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
 365 {
 366         int err = kobject_add(&p->kobj);
 367         if (err)
 368                 return err;
 369         err = kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
 370         if (err)
 371                 kobject_del(&p->kobj);
 372         return err;
 373 }
 374
 375 void cdev_unmap(dev_t dev, unsigned count)
 376 {
 377         kobj_unmap(cdev_map, dev, count);
 378 }
 379
 380 void cdev_del(struct cdev *p)
 381 {
 382         kobject_del(&p->kobj);
 383         kobject_put(&p->kobj);
 384 }
 385
 386 struct kobject *cdev_get(struct cdev *p)
 387 {
 388         struct module *owner = p->owner;
 389         struct kobject *kobj;
 390
 391         if (owner && !try_module_get(owner))
 392                 return NULL;
 393         kobj = kobject_get(&p->kobj);
 394         if (!kobj)
 395                 module_put(owner);
 396         return kobj;
 397 }
 398
 399 void cdev_put(struct cdev *p)
 400 {
 401         if (p) {
 402                 kobject_put(&p->kobj);
 403                 module_put(p->owner);
 404         }
 405 }
 406
 407 static decl_subsys(cdev, NULL, NULL);
 408
 409 static void cdev_default_release(struct kobject *kobj)
 410 {
 411         struct cdev *p = container_of(kobj, struct cdev, kobj);
 412         cdev_purge(p);
 413 }
 414
 415 static void cdev_dynamic_release(struct kobject *kobj)
 416 {
 417         struct cdev *p = container_of(kobj, struct cdev, kobj);
 418         cdev_purge(p);
 419         kfree(p);
 420 }
 421
 422 static struct kobj_type ktype_cdev_default = {
 423         .release        = cdev_default_release,
 424 };
 425
 426 static struct kobj_type ktype_cdev_dynamic = {
 427         .release        = cdev_dynamic_release,
 428 };
 429
 430 static struct kset kset_dynamic = {
 431         .subsys = &cdev_subsys,
 432         .kobj = {.name = "major",},
 433         .ktype = &ktype_cdev_dynamic,
 434 };
 435
 436 struct cdev *cdev_alloc(void)
 437 {
 438         struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
 439         if (p) {
 440                 memset(p, 0, sizeof(struct cdev));
 441                 p->kobj.kset = &kset_dynamic;
 442                 INIT_LIST_HEAD(&p->list);
 443                 kobject_init(&p->kobj);
 444         }
 445         return p;
 446 }
 447
 448 void cdev_init(struct cdev *cdev, struct file_operations *fops)
 449 {
 450         INIT_LIST_HEAD(&cdev->list);
 451         kobj_set_kset_s(cdev, cdev_subsys);
 452         cdev->kobj.ktype = &ktype_cdev_default;
 453         kobject_init(&cdev->kobj);
 454         cdev->ops = fops;
 455 }
 456
 457 static struct kobject *base_probe(dev_t dev, int *part, void *data)
 458 {
 459         char name[30];
 460         sprintf(name, "char-major-%d", MAJOR(dev));
 461         request_module(name);
 462         return NULL;
 463 }
 464
 465 void __init chrdev_init(void)
 466 {
 467         subsystem_register(&cdev_subsys);
 468         kset_register(&kset_dynamic);
 469         cdev_map = kobj_map_init(base_probe, &cdev_subsys);
 470 }